Glossary
Glossary — Telecom & UCaaS Terms
Every term you’ll encounter on a migration project, defined in plain English. When a customer’s IT team uses acronyms, this is where you look.
A
ACO — Avaya Cloud Office. Avaya’s UCaaS product, which is a white-labeled version of RingCentral. Migration to ACO is effectively a migration to RingCentral.
ACD — Automatic Call Distributor. The core of a call center: routes inbound calls to available agents based on rules (skills, queue priority, round-robin, etc.). Often used interchangeably with “contact center.”
ATA — Analog Telephone Adapter. A small device that converts analog telephone signals to SIP/VoIP. Used to connect fax machines, overhead paging, and other analog devices to a UCaaS platform.
ATO — Authorization to Operate. Government term for the formal approval of an IT system for use in a federal environment. Required for FedRAMP deployments.
Auto-attendant — The automated phone menu that answers inbound calls and routes them based on keypad input. “Press 1 for Sales, Press 2 for Support…” Also called IVR.
B
BAA — Business Associate Agreement. HIPAA-required contract between a covered entity (healthcare organization) and a business associate (UCaaS provider) that handles PHI. Required before any HIPAA-compliant deployment.
BLF — Busy Lamp Field. An indicator on a desk phone that shows whether another extension is on a call. Common in reception setups where the front desk needs to see who’s available.
BTN — Billing Telephone Number. The primary number on a carrier account, used to identify the account for porting purposes. Different from the DID being ported.
C
CDR — Call Detail Record. A log entry for each call: originating number, terminating number, duration, timestamp. Required for HIPAA audit logging, call accounting, and billing reconciliation.
CLEC — Competitive Local Exchange Carrier. A carrier that competes with the local phone monopoly (ILEC). Examples: Spectrum Business, Comcast Business, Cox Business. CLECs generally have faster porting than ILECs.
Codec — The algorithm that encodes and decodes voice audio for VoIP transmission. Common codecs: G.711 (high quality, high bandwidth), G.729 (compressed, lower quality), G.722 (HD voice). All parties on a call must support the same codec.
Coverage path — Avaya term. The routing rule that determines what happens when a call isn’t answered: ring to voicemail, forward to another extension, transfer to a hunt group. The UCaaS equivalent is “voicemail overflow” or “no-answer transfer.”
CSR — Customer Service Record. Official document from a carrier showing the current state of a telephone number: account number, BTN, service address, features. Can be requested from the carrier to verify LOA information before submission.
D
DID — Direct Inward Dial. A phone number that routes directly to a specific extension or device. Also called a “TN” (telephone number) or “direct number.” All external-facing numbers are DIDs.
DTMF — Dual-Tone Multi-Frequency. The tones generated by pressing keys on a phone keypad. Transmitted over VoIP using in-band audio, RFC 2833 (RTP-based), or SIP INFO. Matters for IVR navigation, voicemail PINs, and PCI DTMF suppression.
DSCP — Differentiated Services Code Point. A marking in IP packet headers that tells routers to prioritize certain traffic. Voice packets should be marked DSCP EF (Expedited Forwarding, code 46) to ensure they’re prioritized over general internet traffic.
E
E911 — Enhanced 911. The system that routes emergency calls to the correct local PSAP and provides the caller’s location. UCaaS platforms must be configured with accurate E911 addresses for every user and site.
ERL — Emergency Response Location. The address record associated with a user or device in a UCaaS platform for E911 routing. Must match the physical location of the user.
eFax — Fax service delivered over the internet rather than a traditional phone line. The fax number appears normal to senders, but the receiving end converts the fax to an email attachment. The simplest solution for fax migration.
F
FedRAMP — Federal Risk and Authorization Management Program. The US government’s framework for cloud service authorization. Any cloud software used by federal agencies must be FedRAMP authorized. Relevant to GovConnect compliance packages.
FERPA — Family Educational Rights and Privacy Act. US law protecting the privacy of student education records. Applies to educational institutions that receive federal funding.
FOC — Firm Order Commitment. The official date and time a losing carrier commits to releasing a phone number during a port. This is your go-live date for the porting workstream — it cannot be changed on short notice.
FXS — Foreign Exchange Station. The analog port on a PBX that provides dial tone to an analog device (desk phone, fax machine, door phone). When you see “FXS ports” on an Avaya system, it means analog device connections.
G
G.711 — The standard voice codec for VoIP. Uncompressed, high quality, ~64 kbps per call. All platforms support it. Default choice unless bandwidth is severely constrained.
G.729 — A compressed voice codec. Lower quality than G.711 but uses ~8 kbps per call. Useful for low-bandwidth connections, but introduces a small amount of audio degradation.
H
HIPAA — Health Insurance Portability and Accountability Act. US federal law regulating the handling of Protected Health Information (PHI). Healthcare organizations must ensure their UCaaS provider signs a BAA and meets specific security requirements.
Hunt group — A group of extensions that ring sequentially or simultaneously when a number is called. Callers never know which specific extension they’re reaching. Used for departments (Sales, Support) or duty-sharing (after-hours). Called “ring groups” or “call queues” on most UCaaS platforms.
I
ILEC — Incumbent Local Exchange Carrier. The original local phone monopoly (AT&T, Verizon). Typically slower for porting than CLECs.
IVR — Interactive Voice Response. The auto-attendant menu system. “Press 1 for…” IVR and auto-attendant are often used interchangeably, though technically IVR can include more sophisticated features like speech recognition and database lookups.
J
Jitter — The variation in packet arrival timing for VoIP audio. High jitter causes choppy, robotic audio. Target: <20ms. Caused by network congestion, QoS misconfiguration, or poor internet quality.
L
Latency — The delay between a packet being sent and received. One-way voice latency target: <100ms. Above 150ms, users start to notice the delay and “talk over” each other. Caused by distance, routing, or network congestion.
LOA — Letter of Authorization. The document the customer signs to authorize their phone numbers to be ported away from the current carrier. Must include exact account information matching the carrier’s records.
M
MOS — Mean Opinion Score. A standardized measure of voice call quality, rated 1–5 (5 = perfect). Calculated from codec type, latency, jitter, and packet loss. Target: ≥4.0 for business telephony. Below 3.5 is noticeably poor quality.
MPLS — Multiprotocol Label Switching. A private WAN technology used for connecting multiple office locations. Some enterprise customers use MPLS instead of public internet. UCaaS can run over MPLS with proper configuration.
N
NAT — Network Address Translation. The technology that allows multiple devices on a private network to share a single public IP address. Most UCaaS platforms handle NAT via STUN/TURN. Problems arise when SIP ALG manipulates NAT traversal.
P
PSAP — Public Safety Answering Point. The 911 call center. E911 routes your call to the correct PSAP based on your registered location. If E911 is misconfigured, emergency services may go to the wrong location.
PSTN — Public Switched Telephone Network. The traditional phone network — copper lines, carrier circuits, the global telephone infrastructure. UCaaS connects to the PSTN through SIP trunks.
PBX — Private Branch Exchange. The on-premise phone system that manages internal calling and connects to the PSTN. Avaya IP Office, Aura, and MERLIN are PBX systems. UCaaS replaces the PBX.
PCI-DSS — Payment Card Industry Data Security Standard. The security standard for organizations that handle credit card data. If calls involve cardholder information, the phone system may be in scope for PCI.
PHI — Protected Health Information. Any individually identifiable health information regulated by HIPAA.
POE — Power over Ethernet. A method of delivering electrical power through ethernet cables to devices like desk phones, eliminating the need for a separate power adapter.
Q
QoS — Quality of Service. Network configuration that prioritizes voice traffic over general internet traffic. Without QoS, a large download can cause call quality issues. Configured at the router/switch level using DSCP markings.
R
RFC 2833 — The internet standard for carrying DTMF tones in RTP packets. The most reliable method for transmitting keypad tones over VoIP. Most UCaaS platforms use RFC 2833 by default.
RTP — Real-time Transport Protocol. The network protocol that carries the actual voice audio in a VoIP call. SIP sets up the call; RTP carries the audio stream.
RespOrg — Responsible Organization. The entity responsible for managing a toll-free number in the SOMOS database. Porting a toll-free number requires changing the RespOrg.
S
SIP — Session Initiation Protocol. The signaling protocol that sets up, manages, and terminates VoIP calls. SIP defines the call setup; RTP carries the audio.
SIP ALG — Application Layer Gateway for SIP. A feature on many consumer and business firewalls that attempts to inspect and modify SIP packets. In practice, SIP ALG causes far more problems than it solves and should be disabled on all UCaaS deployments.
SIP trunk — A virtual connection between a PBX and the PSTN that carries calls over the internet. SIP trunks replace traditional analog phone lines and T1/PRI circuits. Some UCaaS platforms bundle SIP trunking; others require a separate SIP trunk provider.
SRTP — Secure Real-time Transport Protocol. The encrypted version of RTP. Used by UCaaS platforms to encrypt voice audio in transit. Required for HIPAA and FedRAMP deployments.
SSP — System Security Plan. A document required by NIST and used in FedRAMP authorization. Describes the security controls implemented in an information system.
STUN/TURN — Protocols for NAT traversal in VoIP. STUN (Session Traversal Utilities for NAT) discovers the external IP/port for a device behind NAT. TURN (Traversal Using Relays around NAT) relays media when direct connection isn’t possible. Built into all modern UCaaS platforms.
T
T.38 — The ITU standard for fax-over-IP. Allows fax machines to communicate over VoIP networks by encoding the fax signal in a way that compensates for IP packet loss. Not all UCaaS platforms support T.38 natively.
TLS — Transport Layer Security. The encryption protocol for SIP signaling (SIP-TLS). All UCaaS platforms use TLS for call setup. Required for HIPAA and FedRAMP.
TN — Telephone Number. Same as DID. The actual phone number.
U
UCaaS — Unified Communications as a Service. Cloud-based business phone system: calls, video, messaging, voicemail, and often contact center, all delivered from a cloud provider on a per-user subscription.
V
Voicemail-to-email — A feature that sends an audio file of a voicemail as an email attachment to the user’s email address. Standard on all UCaaS platforms. Must be configured per-user with the correct email address.
W
Webex Calling — Cisco’s UCaaS platform, delivered through CBTS as a channel partner. FedRAMP-authorized for government deployments.
Add new terms as you encounter them. If you heard a term in the field that isn’t here, it belongs here.